There is a well known peripheral control device for educational and industrial robots operated by direct current motors and controlled by a microprocessor. See, SERPENT-SCARA ROBOTS--S.P.E.C. LTD, England. The device contains a multiplexed analog to digital converter and a multiplexed digital to analog converter securing inputs and outputs to the analog voltages with high resolution. The position of each rotary axis is monitored by means of a potentiometric sensor whose output signals through the analog to digital converter is read by the microprocessor which transmits a position task through the digital to analog converter. This task and the voltage from the potentiometric sensor are monitored by a comparator on whose output a voltage is obtained, proportional to the error. The voltage is fed to the input of an operational amplifier whose voltage is controlled by a second digital to analog converter. The gain of the amplifier is programmed by the microprocessor through the digital to analog converter. The operational amplifier output is connected to the input of a second power operational amplifier, securing the current to the direct-current motor. The servocontrol with position feedback thus realized enables program control by the microprocessor of the d.c. motors movement laws, corresponding to the robot axes.
The disadvantages to the known peripheral control device in its application to educational robots control are its complexity, demanding the application of high precision components realized by complicated and unprofitable technology, and the considerable direct participation of the microprocessor in the robot control.
There is also a known educational robot control device, Bulgarian Authorship certificate 38210 for "Educational Robot Control Device", operated by stepper motors, which contains a decoder, connected to address and control buses of a microprocessor whose data and control buses are connected to a signal shaper. Decoder outputs are connected to an input register and an output register which are connected through a dataway to the signal shaper. The input register is connected through a logic check circuit to a power node, consisting of transistor switches, switching the windings of robot stepper motors. An output of the logic check circuit and an output of the external data signals are connected to the inputs of the output register.
A disadvantage of this known device is that it can not perform positioning tasks of more than one step and the microprocessor must feed new, strictly determinate data in the input register for each move to a new step of each stepper motor. With a great number of axes, respectively stepper motors, controlled with different velocity, the microprocessor must spend too much time for execution of the subprograms controlling robot movements. Another disadvantage is that there is no apparatus clearing of the noises in external data signals from sensors and clearing must be realized by means of a computer program after a repeated output register data reading.